Apparatus for chemiluminescent assays

Abstract

Disclosed herein is a device and methods for the rapid chemiluminescence assay of surfaces to detect the presence of microbial contamination. The device and methods are suitable for use by untrained personnel under the relatively harsh and variable conditions found in the field, for example in fast food restaurants and other food preparation areas. The chemiluminescence reaction that is the source of the analytical signal in the disclosed assay device and method is preferably based on a luciferase/luciferin system. The method for sampling disclosed herein comprises the steps of pre-wetting the sampling swab to a level below that of absorptive saturation; wiping a surface to be sampled with the swab with sufficient pressure to expel the wetting solution onto the surface; and, after reducing the pressure exerted on the sampling swab, further wiping the surface to re-absorb the moisture from the surface.

1. A sampling wand for use in a device for a chemiluminescent assay of microbial species on a solid surface, the wand comprising:
 (a) an internal reservoir disposed toward a distal end of the wand; 
 (b) a frangible seal on a bottom surface at a distal end of the wand in fluid communication with the internal reservoir to seal a reagent rinse solution within the reservoir; 
 (c) an external sampling swab comprised of a disc of porous, absorbent polymeric material disposed on the bottom surface at the distal end of the wand with the frangible seal interposed between the sampling swab disc and the reagent reservoir for picking up the microbial species or cellular material from the species upon the surface; 
 (d) an o-ring positioned toward the distal end of the wand being adapted to form a sealing fit between the wand and an internal wall of an inner chamber of a sampling analysis member as the wand moves longitudinally through the inner chamber; 
 wherein when the seal is broken the reagent rinse solution rinses through and from the sampling swab disc to release the microbial species or the cellular material from the sampling swab disc for the assay in the device. 
 
     
     
       2. The sampling wand of  claim 1 , wherein the sampling swab disc has a cylindrical shape. 
     
     
       3. The sampling wand of  claim 2 , wherein the sampling swab disc has a height which is less than a diameter. 
     
     
       4. The sampling wand of  claim 1  further comprising an extracting agent absorbed in the sampling swab disc. 
     
     
       5. sampling wand of  claim 4  wherein the extracting agent is a detergent. 
     
     
       6. The sampling wand of  claim 4  wherein the extracting agent is a cationic detergent. 
     
     
       7. The sampling wand of  claim 4  wherein the extracting agent is benzalkonium chloride. 
     
     
       8. The sampling wand of  claim 7  wherein the benzalkonium chloride is at a concentration of 0.01-1% (wgt/vol). 
     
     
       9. The sampling wand of  claim 1  wherein the reagent rinse solution is a buffer solution. 
     
     
       10. The sampling wand of  claim 9  wherein the buffer solution comprises a neutralizing agent. 
     
     
       11. The sampling wand of  claim 10  wherein the neutralizing agent is selected from the group consisting of non-ionic detergents, cyclodextrins, bovine serum albumin, and combinations thereof. 
     
     
       12. The sampling wand of  claim 1 , wherein the sampling swab disc has a flat surface that maximizes surface area contact between the swab and the surface to be analyzed. 
     
     
       13. The sampling wand of  claim 1  wherein the external sampling swab comprised of a disc of porous, absorbent polymeric material is disposed only on the bottom surface at the distal end of the wand, without a portion of the disc on a side of the wand, with the frangible seal interposed between the sampling swab disc and the reagent reservoir for picking up the microbial species or cellular material from the species upon the surface.